Le Wed, Jun 28, 2023 at 04:24:20PM +0000, RVP a écrit :
> On Wed, 28 Jun 2023, tlaro...@polynum.com wrote:
>
> > But you can't: from the syntax given, \777 is a perfectly valid \77
> > octal sequence followed by the character '7'.
> >
>
> That would be a very surprising way to resolve the ambiguity which is
> present here. There are others when it comes to octal notation:
>
> Single-digit octal escapes can be confused with regexp back-references, so
> POSIX says octal escapes must have at least 2 digits in certain situations.
>
> As for resolving \777 as \777 and not \77'7 is this note in the EXTENDED
> DESCRIPTION for tr(1) (I knew I had read this somewhere in my travels through
> POSIX-land):
>
> \octal
> Octal sequences can be used to represent characters with specific
> coded values. An octal sequence shall consist of a <backslash>
> followed by the _longest_ sequence of one, two, or three-octal-digit
> characters (01234567).
>
> (my emphasis)
>
> What's good for the goose is also good for the gander, I say.
>
OK, in this case if this is specified somewhere, and linked to the way
lexers behave, I will go with this. (It would be good if POSIX in a
revision could suppress all the "singular" explanations of octal, put
a common specified definition in one place, and link to it.)
--
Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
http://www.kergis.com/
http://kertex.kergis.com/
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